1. Field of the Invention
The present invention relates to fifth wheels for coupling tractors and trailers, including over the road tractors and yard tractors, and more particularly to an improved redundant powered apparatus for unlocking the connection to a trailer.
2. Description of the Prior Art
This invention is an improvement on the apparatuses shown in prior U.S. Pat. No. 4,871,182 (1989) to Altherr et al., U.S. Pat. No. 5,028,067 (1991) to Madura, U.S. Pat. No. 5,176,396 (1993) to Hawthorne et al., and U.S. Pat. No. 5,472,223 (1995) to Hawthorne et al., the complete disclosures of which are incorporated by reference herein in their entireties.
Fifth wheel devices include a plate which supports the forward bed plate of a trailer. A king pin is fixed to the trailer bed plate and extends into a center opening of the fifth wheel plate. Fifth wheels have included a pivotally mounted jaw to engage and hold the king pin against horizontal withdrawal. Normally, the jaw closes and is locked on the king pin as the tractor and trailer are brought together. However, there is also a mechanism provided to unlock the jaw to permit horizontal release of a king pin and allow separation of tractor and trailer when the trailer is stationary and the tractor is powered forward. That mechanism usually is operable manually by a driver and includes safeguards so as to avoid accidental release. While there have been earlier designs for automatically releasing fifth wheels, for example see U.S. Pat. No. 2,471,854 to Bies et al., experience with over the road hauling during the last several decades has developed an abundance of caution against automatic operation of fifth wheels and, largely for reasons of safety, the industry had disdained release mechanisms using accessory power. Thus, modern over the road fifth wheels, such as that shown in U.S. Pat. No. 4,871,182, have incorporated unlocking features that are solely operable from outside the tractor cab and have not been regarded as suitable for operation with accessory power. However, as trucks have tended to become larger in size and incorporate aerodynamic features it has become more difficult to reach the operation mechanism; this problem is exacerbated for persons of small stature. Furthermore, even for tall persons, manual operation has caused soiling and tearing of clothing and, for some, may have contributed to back strains and the like.
The inventions disclosed in U.S. Pat. Nos. 5,028,067, 5,176,396 and 5,472,223 have met the need for safe release mechanisms with accessory power. The accessory uncoupling apparatuses disclosed in those patents have been redundant systems, operable to manually override the manually operable unlocking mechanism. The accessory uncoupling apparatuses have also permitted remote activation of the jaw unlocking mechanism.
Two of those accessory uncoupling apparatuses, disclosed in U.S. Pat. Nos. 5,176,396 and 5,472,223, have utilized a reciprocable power device to move a cam against a fifth wheel operating rod. In both of these devices, the cam is connected to both a reciprocable power device and to a separate guide shaft. The guide shaft is slidable along a guide-way, and the guide way and reciprocable power device are connected to a mounting bracket. A cam return means, such as a spring, has also been included. The mounting bracket, cam, reciprocable power device, cam return means, guide shaft and guide cam are fabricated into an assembly, and the fabricated assembly is attached to a web on the underside of a fifth wheel plate to retrofit an existing fifth wheel assembly with the powered unlocking system. Although such a system has been successful, it has manufacturing disadvantages in the number of parts and the time and expense involved in fabricating the assembly.